1. Field of the Invention
The present invention relates to a key switch device having a guide member provided with two link members mutually movably connected, the guide member guiding a vertical movement of a key top to thereby effect a switching operation. In particular, the present invention relates to a key switch device having a circuit board with a circuit pattern for performing a switching operation by the circuit pattern, the circuit board being disposed below a key top, and a mounting member for movably supporting each lower end of two link members of a guide member, the mounting members being fixed on the circuit board by a predetermined fixing manner, thereby the key switch device can reduce manufacturing cost and increase design flexibility of a keyboard provided with a plurality of the key switch devices, and achieve weight reduction of the keyboard.
Further, the present invention relates to a keyboard and an electronic apparatus in which the above key switch devices are arranged.
2. Description of Related Art
Conventionally, there have been proposed key switch devices each having a guide member constructed of a pair of link members mutually movably connected in an intersecting state, and the guide member serves to guide the vertical movement of a key top to effect a switching operation in association with the vertical movement of the key top. For example, such a key switch is disclosed in Japanese utility model application laid-open No. Hei 2-5236. This key switch is provided with a key top, an upper holder attached to an underside of the key top, a first lower holder and a second lower holder attached to a printed substrate, and two rectangular frames connected to each other in an X-shaped configuration as viewed in side elevation, which are disposed between the key top and the printed substrate.
In this key switch, an upper portion of one of the rectangular frames is slidably supported in the upper holder between the lower surface of the key top and the upper holder, while leg portions of the rectangular frame are rotatably supported in the first lower holder. On the other hand, an upper portion of the other rectangular frame is rotatably supported in a groove of the upper holder, while leg portions of the rectangular frame are slidably supported in the second lower holder. Furthermore, a rubber switch is disposed on, the printed substrate, and a convex portion of the key top, projecting downward, is engaged with the rubber switch. The rubber switch is provided with a movable contact disposed corresponding to a fixed contact disposed on the printed substrate.
The above key switch is configured such that the key top is vertically moved with its horizontal position being maintained, no matter which portion of the key top is depressed by an operator. Accordingly, the movable contact of the rubber switch engaged with the key top is made into contact with the fixed contact of the printed substrate whenever the rubber switch is pushed upon depression of the key top, thus effecting a switching operation.
However, in the above key switch disclosed in Japanese utility model application laid-open publication No. Hei 2-5236, the first and second lower holders attached to the printed substrate are all inserted in mounting holes formed in the printed substrate (see FIGS. 2 and 4 in the publication) and fixed therein. Therefore, each lower end of the first and second lower holders is made projecting downward from a lower surface of the printed substrate.
Such projecting lower ends of the first and second lower holders may cause a difficulty in thickness reduction of the key switch and be against actual circumstances that the reduction of the thickness of a key switch is promoted.
To conform the need of reduction in size and thickness of a keyboard with a sufficient key stroke being ensured, applicant of the present invention proposed a key switch device which is disclosed in U.S. Pat. No. 5,504,283, in which an electrical circuit pattern is formed on an insulating layer provided on a metal substrate, and four mounting portions are formed integrally with the substrate by pressing and disposed surrounding a fixed contact pattern in the circuit pattern. Two of the four mounting portions having arc shapes are used as rotatably supporting portions, and the other two having long-hole shapes are used as slidably supporting portions.
In the above switch device, a guide supporting member constructed of two link members which are mutually rotatably connected is disposed between the key top and the substrate. A support shaft formed between upper ends of the two link members is rotatably supported in the connecting portions formed on the underside of the key top and support pins formed at lower ends of the link member are slidably supported in the slidably supporting portions of the substrate support pins formed at upper ends of the other link member is slidably supported in the connecting portions formed on the underside of the key top and a support shaft formed between lower ends of the link member is rotatably supported in the rotatably supporting portions of the substrate.
In the key switch disclosed in the U.S. Pat. No. 5,504,283, the metal substrate is formed integrally with the mounting portions (supporting portions) by pressing, the mounting portions serving to slidably or rotatably support the support pins or Shafts disposed on the lower parts of the link members. Thus, this realizes a key switch device which can ensure a sufficient key stroke and reduce the size of the keyboard, especially the thickness thereof.
However, a predetermined pressing work to integrally form the mounting portions with the substrate needs a relatively large pressing die in order to form the mounting portions in the whole area of the substrate. Since the pressing die is expensive, the cost of the key switch device is increased in association therewith.
Furthermore, specifications such as the placement manner of key switches are generally determined in various countries where the key switches are used. If the key switch device is manufactured based on each of the specifications in the countries where the key switch device is to be used, plural types of a pressing die must be prepared to perform a suitable pressing work on a substrate in response to the respective specifications. Accordingly, the preparation of plural pressing dies, each being inherently expensive in cost, may cause the increase in cost of the key switch device.
Furthermore, the metal substrate itself used in the above key switch device is considerably heavy, so that the whole key switch device increases in weight. This obstructs weight reduction of the key switch device.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a key switch device having mounting members for movably supporting lower ends of two link members of a guide member guiding vertical movement of a key top, the mounting members being fixed on a film sheet for performing a switching operation, by a predetermined one of various fixing manners, thus eliminating the need of a pressing die used in the prior art, so that the key switch device can reduce the manufacturing Cost, increase the design flexibility of a keyboard provided with a plurality of the key switch devices, and achieve weight reduction of the keyboard.
To achieve the purpose of the invention, according to one aspect of the present invention, there is provided a key switch device including
a key top;
a circuit board disposed below the key top, the circuit board having a switching circuit formed thereon;
a guide member provided with a first link and a second link which are mutually movably connected;
a switching member which performs a switching operation with the switching circuit on the circuit board in association with a vertical movement of the key top;
a first shaft formed at a lower end of the first link;
a second shaft formed at a lower end of the second link; and
a mounting member for movably supporting both the first and second shafts, the mounting member being fixed on an upper surface of the circuit board.
In the above key switch device according to the present invention, a circuit board having a switching circuit is used. On the circuit board, a mounting member made is fixed to the circuit board so that the first shaft of the first link and the second shaft of the second link of the guide member are movably supported. It is therefore unnecessary to form supporting portions in the support plate by a press working. Accordingly, the need of a pressing die used in the press working is eliminated, and the manufacture cost of the key switch device can be reduced.
Even if the specifications of the keyboard provided with the key switch devices are different on a country-to-country basis, it is sufficient to form a fixing area constructed from a metal land patterns in response to the specifications and to fix the mounting members on the land patterns. This can increase the design flexibility of the keyboard having the key switch devices without preparation of a pressing die for the different specifications on a country-to-country basis.
The mounting member of the key switch device may be fixed to the metal land pattern on the circuit board by soldering. The use of circuit board may not necessarily require a support plate, which will enable the weight reduction of the key switch device.
The circuit board is preferably a rigid circuit board. The board having the great rigidity can support the entire keyboard provided with a plurality of the key switch devices, so that the support plate may be eliminated.
According to another aspect of the present invention, there is provided a key switch device including;
a key top;
a transparent membrane switch member disposed below the key top;
a guide member provided with a first link and a second link which are mutually movably connected;
a switching member which performs a switching operation of the membrane switch member in association with a vertical movement of the key top;
a first shaft formed at a lower end of the first link;
a second shaft formed at a lower end of the second link;
a mounting member for movably supporting both the first and second shafts, the mounting member being fixed on an upper surface of the membrane switch member; and
an electro-luminescent sheet disposed below the membrane switch member, the electro-luminescent sheet backlighting the key top when a predetermined voltage is applied to the electro-luminescent sheet.
In the above key switch device according to the present invention, the mounting member is fixed on the upper surface of the membrane switch member and movably supports the first and second shafts formed at the lower ends of the first and second links respectively of the guide member for guiding the vertical movement of the key top. And the electro-luminescent sheet, which backlights the key switch when a predetermined voltage is applied thereto, is disposed below the membrane switch sheet. Accordingly, similarly to the above key switch device, the support plate has no need to be integrally formed with supporting portions for mounting the guide member by a press working and the like. This eliminates the necessity of an expensive pressing die, thus enabling the reduction of manufacturing cost of the key switch device.
Even if the specifications such as the placement of the key switch devices in a keyboard are different according to countries where the key switch device is to be used, it is sufficient to fix the mounting members on the membrane switch member in agreement with the specifications on a country-to-country basis. This can increase the design flexibility of a keyboard having the key switch devices without preparation of a pressing die for the specifications in each country.
Since the mounting member is fixed on the upper surface of the membrane switch member, a support plate may be eliminated, which achieves the weight reduction of the key switch device.
Further, in addition to the above effects, since the electro-luminescent sheet is disposed below the membrane switch member and backlights the key top when a predetermined voltage is applied thereto, the key switches arranged on the keyboard can be easily identified, even in darkness or low ambient light conditions, so that key operation can be easily performed in such conditions. And in case that the key switches are used in a projector, which is usually used in darkness or low ambient light conditions, the key switches will ensure the proper and smooth projector operations with the electro-luminescent sheet backlighting the key tops in the key switches.
According to further another aspect of the present invention, there is provided a keyboard provided with a key switch device including;
a key top;
a circuit board disposed below the key top, the circuit board having a switching circuit formed thereon;
a guide member provided with a first link and a second link which are mutually movably connected;
a switching member which performs a switching operation with the switching circuit on the circuit board in association with a vertical movement of the key top;
a first shaft formed at a lower end of the first link;
a second shaft formed at a lower end of the second link; and
a mounting member for movably supporting both the first and second shafts, the mounting member being fixed on an upper surface of the circuit board.
And according to further another aspect of the present invention, there is provided with an electronic apparatus having a keyboard provided with a key switch including:
a key top;
a circuit board disposed below the key top, the circuit board having a switching circuit formed thereon;
a guide member provided with a first link and a second link which are mutually movably connected;
a switching member which performs a switching operation with the switching circuit on the circuit board in association with a vertical movement of the key top;
a first shaft formed at a lower end of the first link;
a second shaft formed at a lower end of the second link; and
a mounting member for movably supporting both the first and second shafts, the mounting member being fixed on an upper surface of the circuit board.
The above key switch devices utilized in the keyboard and the keyboard used in the electronic apparatus have the same feature as that of the key switch device described above. Therefore, the same effects described with reference to the above key switch device can be obtained.